This invention relates generally to the repair of gas turbine engines and more particularly to the repair of stationary seals used in such engines.
Gas turbine engines have numerous air seals intended to control the flow of air between various engine components. One common type of seal comprises an arcuate support member which carries a stationary sealing member, for example an abradable or honeycomb material, which is disposed in close proximity to circumferential seal teeth on a rotating member to create a tortuous flowpath, reducing air leakage past the seal. If the radial clearance between the parts of the seal should be reduced, for example in the case of transient engine operating conditions, the seal teeth can abrade or cut into the sealing member without generating excessive heat or wear in the seal teeth. Thus, the stationary portion of the seal is sacrificial.
In the interests of economy these types of seals are repaired when the stationary sealing member is excessively worn or damaged. The seals are typically repaired by cutting away a portion of the support member to which the sealing member is attached and welding a replacement portion of the support member to the remaining portion. A new sealing member can then be attached to the repaired support member.
Unfortunately, the required cutting operation can cause the support members, which are relatively thin cylindrical or band-shaped structures, to become distorted; for example the support member itself may go out-of-round, or a mounting flange that is part of the support member, which should be flat, may warp. The various prior art methods used to correct the distortion of the support member prior to welding can lead to cracking and local distortion of the support member. Also, in order to avoid contamination of the welds the support member is typically sealed with a heat resistant tape to contain an inert gas blanket. Applying this tape is time consuming and the tape does not always adequately protect the joint. Furthermore, the support member experiences diametrical shrinkage as a result of the welding process which must be corrected by expanding the support member in a subsequent operation. This typically requires a second piece of equipment in addition to the fixture used to hold the support member while it is welded.
Accordingly, there is a need for a method of repairing annular components with reduced distortion of the component and consistent weld quality. In particular, there is a need for a fixture that will facilitate such repair of annular components
The above-mentioned need is met by the present invention, which provides a multifunctional weld fixture having a base for receiving a component and a plurality of locator tabs disposed around its outer edge. A circumferential array of expansion feet are movably attached to the top surface of the base. A disk-shaped wedge is disposed in sliding engagement with the expansion feet. A cover supports a portion of the component and seals against the component to create an enclosed plenum. The same fixture may be used to expand the component to compensate for shrinkage after the weld is compete.
The present invention and its advantages over the prior art will become apparent upon reading the following detailed description and the appended claims with reference to the accompanying drawings.